The invention relates to a television camera comprising a control circuit for controlling the electron beam current intensity in at least one pick-up tube, the control circuit having an input which is connected to a pick-up tube output for producing a picture signal, and an output which is connected to a pick-up tube input for controlling the intensity of the electron beam current, the control circuit including, between the input and the output, a picture signal amplifier comprising a signal amplifier transistor which is biased by means of its base, an emitter-follower transistor and a signal limiter provided between the junction of the collector of the signal amplifier transistor and the base of the emitter follower transistor and a voltage terminal, the signal limiter including a diode and a zener diode which are interconnected.
Such a television camera is disclosed in U.S. patent application No. 191,099 filed Sept. 26, 1980 which is a continuation of 958,318 filed Nov. 6, 1978, now abandoned. In practice the above-described control circuit proved to be very satisfactory for studio and outdoor recording. However, in extreme circumstances, with very great contrasts such as may occur in outdoor recording under a bright blue sky, oscillations may be produced in the positive feedback control loop which are displayed as horizontal lines in the picture. The risk of oscillations is reduced when the quiescent biasing current is increased, but this increase introduces defocussing which reduces the resolution of the picture on display.